Magnesium and aluminum soap grease



Patented Dec. 16,1941

MAGNESIUM AND ALUMINUM SOAP GREASE Herbert C. Freuler, Berkeley, Calif.,

Union Oil Company of California, Calii'., a corporation of Californiaassignmto Los Angeles,

No Drawing. Application November 18, 1938, Serial No. 241,221

18 Claims.

This invention relates to improved aluminum soap greases and theprincipal object of the invention is to provide means whereby suchgreases, such as those derived from the admixture of aluminum stearatewith mineral oil and containing substantial amounts of soap, will befree of the usual objectionable tendency to assume a rubbery or gel-likestructure when employed for lubrication at temperatures elevatedsomewhat above normal.

Aluminum soap greases are well known in the art and are desirableincommerce because of their smooth, transparent chcaracteristics and highcompatibility with the oil used and also because they are. resistant tothe action of water and have melting points higher than thewaterresistant calcium soap greases, thereby distinguishingfrom calciumsoap greases by reason of said higher melting point and from sodium soapgreases by reason of their resistance to water. However, aluminum soapgreases, even when containing small quantities of soap, such as 2% or 3%.of aluminum stearate, tend to assume a gel-like or rubbery structurewhen heated to temperatures of 160 F. to 180 F. and when subsequentlycooled, are granular or rubbery for a' period of from 12 to 24 hoursbefore reas'suming their typical grease body. This is very objectionableand tends to impair the lubricating efficiency of the grease moreespecially when large proportions of the soap, such as% or more, areused. I have discovered that by incorporating small sistance thansimilar greases prepared by the use of aluminum stearate alone.

The present invention may, therefore, be stated as residing in aluminumsoap greases containing a smaller proportion of magnesium soap thanaluminum soap such proportion depending upon the percentage of totalsoap in the finished grease and upon the characteristics desired in thefincontain aluminum soap, such as aluminum stearate or aluminum oleate,and magnesium soap, such as magnesium stearate, the latter being insmaller proportion than the aluminum soap but in a quantity sufficientto completely overcome or partially overcome the gelation tendency ofthe aluminum soap, the total proportion of the combined aluminum andmagnesium soaps being that required to yield the grease' consistencydesired.

percentages of magnesium soap into lubricants containing aluminum soap,this objectionable tendency to gel or form a rubbery structure atslightly elevated temperatures can be overcome. For example, suchtendency toward gelation or the development of a rubbery structure maybe overcome by the addition, for example, of from 0.1% to 5% ofmagnesium stearate to greases containing from 2% to 15% of aluminumstearate,

the greases being compounded with any appropriate mineral lubricatingoil in accordance with ordinary or preferred procedures. Furthermore, Ihave discovered thatwhen using a mixture of aluminum and magnesium soapsin the preparation of agrease, it is necessary to employ a slight- 15? geater in other words, of the'same A; S. T. M. penetration, and aluminumstearate alone. I have discovered I proportion of soap to mineral oil.inv order to obtain greases of the same stiffness or,

cooledto room temperature.

One desirable method of manufacture consists in incorporating powderedmagnesium soap in desired proportion into powdered aluminum soap beforeaddition to oil to yield grease. The powdered soap mixture, afterthorough blending of the two soaps, is then admixed in the desiredproportion in a suitable mineral lubricating oil,

as by means of agitation at ordinary tempera- 'tures, After uniformmixing and the elimination of any soap lumps which may form, theoil-soap mixture is then heated to an elevated temperature until anapparently clear solution is formed.

Such a temperature may be around 320 F. or within a range of about 280F. to 350. F. as understood -in the art. The hot grease productis thendrawn into appropriate receptacles and Again, it is possible to preparea hot oiland aluminum soap mixture and add to this the reas greasescompounded from mineral oil that, as a result of being able toincrease'the soap'content, the resultant magnesium-aluminum soap greasespossess a greater degree of water're quired quantity of magnesium soap,the mixture beingagitated and heatingbeing continued until a suitableproduct is formed. Again the aluminum soap, the magnesiumsoap and thelubricating oil 'may all be introduced into a compounding kettle, mixedat atmospheric temperature 5 andthen heated, for example to around 300F.,

for 30 minutes or until an apparently clear solu- I v tion is formed.

In operating the soap ratios would be adjusted according to the resultsrequired. For example about 0.1% of magnesium stearate may be introducedinto a light aluminum soap grease containing, for example, 4% of.aluminum stearate and the soap product formed as above indicated, withthe resultant formation of a light grease substantially free from theabove mentioned gel type structure. Again a heavier grease containing15% soap may be so produced, of which aluminum stearate will constituteabout 13% and 'magneslum stearate about 2%. A smaller quantity ofmagnesium stearate will result in a product having some tendency tobecome rubbery, whereas 3% or 4% of magnesium stearate will completelyinhibit the gelation tendency with some consequent decrease in thethickening power of the aluminum soap.

' The aluminum soap selected may be any appropriate aluminum soap suchas aluminum stearate, aluminum oleate, aluminum naphthenate, aluminumpalmitate or other suitable soap; and the magnesium soap may bemagnesium stearate, magnesium naphthenate, magnesium oleate. magnesiumpalmitate or other appropriate oilsoluble magnesium soap. Thelubricating oil may be any ordinary or preferred type of lubricating oilof paraflinic or naphthenic or mixed base type, although, ordinarily, Iprefer to use naphthenic base or western mineral lubricating oilsbecause of their superior soap-dissolving characteristics.However,satisfactory greases have been prepared by compounding a'mixtureof aluminum and magnesium soaps with crystal oil. The ability oi" thealuminum soap greases to receive materials, such as rubber latex or highmolecular weight hydrocarbon polymers, in small .amounts (e. g. 0.1%) togive a final product having a stringy" characteristic, is not aifectedby the presence of the magnesium soap hereof.

As an example of greases which may be prepared by the present invention,the following ingredients were thoroughly admixed in the proportionsindicated at atmospheric temperature, and then heated, while stirring,to approximately 300 F., at which temperature the batch was maintainedfor about 30 minutes and then drawn into pans and cooled to roomtemperature:

Aluminum stearate per cent 13.0 Magnesium stearate do 2.0Naphthenic-base lubricating oil do L 85.0

The characteristics of the mineral oil were as follows:

Gravity, A. P. I 18.5

' Saybolt Universal viscosity at 210 F.

seconds-.. 67 Color, N. P. A '7 The product was allowed to cool to roomtem perature over a period of about 12 hours and was then worked througha gear pump whereupon it possessed an A. S. T. M. penetration at 235 at-77 F., as against an A. S. T. M. penetration of 195 for the unworkedgrease at"l'l F.

As another example, the following ingredients were. compounded in amannersimilar to that described above for the purpose of producing agrease in accordance with this invention:

The characteristics of the crystal oil were as follows:

seconds-.. 340 I The A. S. T.. M penetration of the worked grease was330 at 77 F.

The above disclosures are furnished as illustrative of the genericinvention and are not intended as necessarily limiting.

1 I claim: I

1. A lubricating grease comprising as important constituents minerallubricating oil, aluminum soap in quantity to thicken the oil and impartgrease-like characteristics, and magnesium soap in proportions smallerthan the aluminum soap and suilicient to control gelling tendencies ofthe alumium; soap.

2. A lubricating grease. comprising a major proportion of; minerallubricating oil, a minor proportion of aluminum stearate to thicken theoil and impart grease-like characteristics, and magnesium soap inproportions less than that of the aluminum soap to reduce the tendencyof the aluminum soap to impart gel characteristics, the grease havingimproved water-resisting characteristics over greases containingaluminum stearate alone.

3. A grease comprising a naphthenic base mineral lubricating oil,aluminum soap sufficient to thicken the oil to grease consistency, and asmaller porportion of magnesium soap to reduce uents a minerallubricating oil, between about "2% and 15% of aluminum soap to thickenthe oil and impart grease-like characteristics, and btween about 0.1%and 5% ofimagnesium soap to reduce the tendency of the aluminum soap toimpart gel characteristics.

5. A lubricating grease comprising as principal constituents mineral'lubricating oil, between about 2% andabout 15% of an aluminum soap tothicken the oil and impart grease-like characteristics with gellingtendencies, and magnesium soap approximating one-tenth oi the aluminumsoap to overcome the gelling tendencies of the aluminum soap. 1

6. A- lubricating grease comprising as important constituents minerallubricating oil, a quantity of aluminum stearate suiilcient to impartgrease-like characteristics and at. the same time impart gellingtendencies and, a minor proportion of magnesium stearate with respect tothe aluminum stearate to overcome gelling tendencies imparted by thealuminum stearate, the soaps being present in the order of between about3% and about 4% of magnesium stearate in a total soap content of about15%.

7. A lubricating grease comprising as important constituents a majorproportion of mineral lubricating oil, a minor proportion of aluminumstearate to thicken the oil and impart grease-like characteristics, anda minor proportion of magnesium stearate to control gelling tendenciesof the aluminum stearate within ratio limits .between about 2 parts ofmagnesium stearate to 13 parts of aluminum stearate and 5 parts ofmagnesium stearate to 15 parts of aluminum stearate.

Aluminum stearate -per cent-.. '11.0

8. A method for preparing aluminum stearate rease substantially freefrom gelling tendencies and containing magnesium. stearate comprisingcommingling aluminum stearate '13. A grease according to stearate atnormal temperatures, admixing mineral lubricating oil with said soap atnormal temperatures, heating the oil-soap-mixture to a temperaturewithin a range between about 280 to 350 F. and drawing the grease, thealuminum stearate being in quantities suflicient to impart grease-likeconsistency to the oil, and the magnesium stearate being in smalleramount to reduce the tendency of the aluminum stearate to impart gelcharacteristics.

9. A grease according to claim 1 containing a small proportion of a highmolecular weight hydrocarbon polymer to impart stringy characteristics.

10. A grease according to claim 4 containing a small proportion 01 ahigh molecular weight hydrocarbon polymer to impart stringycharacteristics.

11. A grease according to claim 6 containing a small proportion of ahigh molecular weight hydrocarbon polymer to impart stringycharacteristics. I v

12. A grease according to claim 3 to which a minor proportion of rubberlatex has been added to impart stringy characteristics.

rubber latex in the order of 0.1%

to impart stringy characteristics.

claim 7 containing,

14. A grease according to claim 2 containing in the order of 0.1% of ahigh molecular weight hydrocarbon polymer to impart stringycharacteristics to the product.

' 15. A grease according to claim 5 containing in the order of 0.1% of ahigh molecular weight hydrocarbon polymer to impart stringycharacteristics to the product.

16. A grease according to claim 7 containing a small proportion of ahigh molecular weight hydrocarbon polymer capable of imparting stringycharacteristics.

17. A grease comprising as important constituents mineral lubricatingoil, aluminum soap to thicken the oil and impart grease-likecharacteristics, and a minor proportion of magnesium soap to controlgelling tendencies of the aluminum soap in the proportion of aboutone-twentieth to one-third of the magnesium soap based on the aluminumsoap.

18. A grease according to claim 17 containing HERBERT c, FREULER.

